In the present study, the Johnson-Cook damage model is proposed as a comprehensive damage criterion to predict all types of probable failures in tube hydroforming process. Also, the Johnson-Cook material model is used to predict the profile of hydroformed tubes and their dimensions. The validity of numerical results was verified using experimental results obtained in this study. Moreover, because of the importance of friction force in this process, existing between the tube and die, the friction coefficient is determined using the ring compression test, separately. The comparison of experimental and numerical results shows that Johnson-Cook damage model can predict all of the possible failures in tube hydroforming process correctly, both in terms of location and loading conditions. And this model does not predict any failure if, the tube is hydroformed perfectly. Additionally, it was cleared that the Johnson-Cook material model is a proper model to predict the profile of hydroformed tubes with remarkable accuracy. Also, it was found that the loading path and creation of a proper wrinkling have a determinative and vital role in the prosperity of the process.

中文翻译：

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管材液压成形综合损伤判据

在本研究中，Johnson-Cook 损伤模型被提出作为综合损伤准则来预测管材液压成形过程中所有类型的可能失效。此外，Johnson-Cook 材料模型用于预测液压成型管的轮廓及其尺寸。利用本研究中获得的实验结果验证了数值结果的有效性。此外，由于摩擦力在该过程中的重要性，存在于管子和模具之间，摩擦系数使用环压缩试验单独确定。实验和数值结果的比较表明，Johnson-Cook 损伤模型可以正确预测管材液压成形过程中所有可能的故障，无论是位置还是加载条件。并且这个模型不能预测任何失败，如果，管子是完美的液压成型。此外，Johnson-Cook 材料模型是一个合适的模型，可以非常准确地预测液压成型管的轮廓。此外，还发现加载路径和适当皱纹的产生对过程的繁荣具有决定性和重要作用。